Predicting Breast Cancer Endocrine Responsiveness Using Molecular Imaging

Dedicated Breast Gamma Camera Imaging and Breast PET: Current Status and Future Directions

Recent advances in nuclear medicine instrumentation have led to the emergence of improved molecular imaging techniques to image breast cancer: dedicated gamma cameras using γ-emitting ^99mTc-sestamibi and breast-specific PET cameras using ¹⁸F-fluorodeoxyglucose. This article focuses on the current role of such approaches in the clinical setting including diagnosis, assessing local extent of disease, monitoring response to therapy, and, for gamma camera imaging, possible supplemental screening in women with dense breasts. Barriers to clinical adoption and technologies and radiotracers under development are also discussed.

Imaging performance in guiding response to neoadjuvant therapy according to breast cancer subtypes: A systematic literature review

Monitoring therapeutic response to neoadjuvant chemotherapy(NAC) is likely to improve NAC effectiveness in breast cancer(BC). Imaging performance seems to vary per tumour subtype(by ER and HER2 status), therefore we performed a systematic review on subtype specific imaging performance in monitoring NAC in BC. Studies examining imaging performance in predicting pathologic complete response(pCR) during NAC in BC subtypes were selected. Per study, negative- and positive predictive value, sensitivity(se) and specificity(sp), AUC and accuracy were derived. Fifteen/106 articles were included. Inter-study variability was revealed in: monitoring interval, response and pCR definitions. In ER-positive/HER2-negative BC, ¹⁸1F FDG-PET/CT showed se/sp of 38%-89%/74%-100%, MRI showed se/sp of 35%-37%/87%-89%. In triple negative BC, ¹⁸1F FDG-PET/CT showed se/sp of 0%-79%/95%-100%. ¹⁸1F FDG-PET/CT showed in ER-positive/HER2-positive BC se/sp of 59%/80% and in ER-negative/HER2-positive 27%/88%. Evidence on imaging performance in monitoring NAC according BC subtypes is lacking. Consensus should be reached in: definitions of pCR, response and monitoring interval before starting well-designed studies.

Pharmacodynamic imaging guides dosing of a selective estrogen receptor degrader

PURPOSE

Estrogen receptor (ER) targeting is key in management of receptor-positive breast cancer. Currently, there are no methods to optimize anti-ER therapy dosing. This study assesses the use of 16α-(18)F-fluoroestradiol ((18)F-FES) PET for fulvestrant dose optimization in a preclinical ER(+) breast cancer model.

EXPERIMENTAL DESIGN

In vitro, (18)F-FES retention was compared with ERα protein expression (ELISA) and ESR1 mRNA transcription (qPCR) in MCF7 cells (ER(+)) after treatment with different fulvestrant doses. MCF7 xenografts were grown in ovariectomized nude mice and assigned to vehicle, low- (0.05 mg), medium- (0.5 mg), or high-dose (5 mg) fulvestrant treatment groups (5-7 per group). Two and 3 days after fulvestrant treatment, PET/CT was performed using (18)F-FES and (18)F-FDG, respectively. ER expression was assessed by immunohistochemistry, ELISA, and qPCR on xenografts. Tumor proliferation was assessed using Ki67 immunohistochemistry.

RESULTS

In vitro, we observed a parallel graded reduction in (18)F-FES uptake and ER expression with increased fulvestrant doses, despite enhancement of ER mRNA transcription. In xenografts, ER expression significantly decreased with increased fulvestrant dose, despite similar mRNA expression and Ki67 staining among the treatment groups. We observed a significant dose-dependent reduction of (18)F-FES PET mean standardized uptake value (SUV(mean)) with fulvestrant treatment but no significant difference among the treatment groups in (18)F-FDG PET SUV(mean).

CONCLUSIONS

We demonstrated that (18)F-FES uptake mirrors the dose-dependent changes in functional ER expression with fulvestrant resulting in ER degradation and/or blockade; these precede changes in tumor metabolism and proliferation. Quantitative (18)F-FES PET may be useful for tracking early efficacy of ER blockade/degradation and guiding ER-targeted therapy dosing in patients with breast cancer.

Optimization of the preparation of fluorine-18-labeled steroid receptor ligands 16alpha-[18F]fluoroestradiol (FES), [18F]fluoro furanyl norprogesterone (FFNP), and 16beta-[18F]fluoro-5alpha-dihydrotestosterone (FDHT) as radiopharmaceuticals

Fluorine-18-labeled steroid receptor tracers, 16α-[(18)F]fluoroestradiol (FES), [(18)F]fluoro furanyl norprogesterone (FFNP), and 16β-[(18)F]fluoro-5α-dihydrotestosterone (FDHT), are important imaging tools for studies of breast and prostate cancers using positron emission tomography (PET). The automated production of these ligands with high specific activity (SA) as radiopharmaceuticals requires modification and optimization of the currently reported methods. [(18)F]FES with high SA was synthesized in over 60% radiochemical yield (RCY) at the end of synthesis (EOS) using a small amount of precursor (1) (as low as 0.3 mg) and 1 M H2SO4 for deprotection of the intermediate (2). [(18)F]FFNP was synthesized in up to 77% RCY at EOS using the triflate precursor (4) at room temperature or in 25% RCY using the mesylate precursor (6) at 65°C. Both methods are highly reproducible and afford high SA. [(18)F]FDHT was synthesized by radiofluoride incorporation at room temperature, reduction with NaBH4 , and deprotection with HCl/acetone, giving [(18)F]FDHT in up to 75% yield (RCY). All of these methods can be easily translated to automated production. The information provided here will aid in the development of automated production of these steroid receptor tracers with high or improved yields, optimal SA, and ease of processing for research and clinical use.